Breakthrough For Short Term Gene Therapy

Researchers have developed a new and improved way of delivery mRNA into cells - allowing temporary expression of a therapeutic protein

Gene therapy is a broad term for many different techniques. Within these there are 2 main strategies: delivery of DNA or delivery of mRNA. Delivery DNA, as a genetic code, allows the cell to translate this into mRNA, which is then translated into a protein. Genes can either be integrated into the genome, making them permanent additions even after cell division, or integrated within a DNA circle that remains in the cell as long as it lives but is not passed down during cell division. The second of these is by far the most popular option right now, as there are fears of permanent integration causing cancer in certain cases (although this is now much better understood). An alternative option of the delivery of mRNA, which is directly translated into a protein within the cell.

The advantage of mRNA delivery

While gene delivery methods are more permanent, they are also more expensive and commonly involve viral vectors to deliver the payload into cells. In many cases long term expression of a gene is not desirable, and a short burst of expression might allow rejuvenation in a controlled manner. After a while mRNA degrades in cells, and so doesn't stick around in the same way DNA does. mRNA treatments are also theoretically cheaper and can be administered in a more localised manner. The main problem with this strategy is that it's difficult to deliver mRNA into cells in the first place. mRNA is negatively charged, while the cell membrane is positively charged. 

A breakthrough in delivery

In order to shuttle mRNA through the cellular membrane, it needed a positively charged casing that would detach once inside the cell. To solve this problem researchers came up with something called charge-altering releasable transporters (CARTs). These molecules were designed to shift charge once inside the cell; becoming neutral and gradually biodegrading. Following their transformation from polycations to polyneutrals, these CARTs are excreted from the body.

The research team tested this approach using a glowing firefly protein. The mRNA code for the protein was successfully delivered in mice and did indeed begin to glow. 

"It's almost a childlike enthusiasm we have for this. The code for an insect protein is put into an animal and that protein is not only synthesized in the cells but it's folded and it becomes fully functional, capable of emitting light. What distinguishes this polycation approach from the others, which often fail, is the others don't change from polycations to anything else. Whereas, the ones that we're working with will change from polycations to neutral small molecules. That mechanism is really unprecedented"

A step forward

This is a simple, elegant solution that could facilitate many new kinds of therapies. Temporary gene therapy has a number of advantages and can be utilised for things like vaccinations and immunotherapy. It could also be used to trigger safer, short term exposure to factors that wind back the clock in cells. 

"Gene therapy has been held up as a silver bullet because the idea that you could pick any gene you want is so alluring. With mRNA, there are more limitations because the protein expression is transient, but that opens up other applications where you wouldn't use other types of gene therapy"

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